Optimization of process parameters in microbial bio-hydrogen production from waste wheat starch as substrate by dark and photo fermentation

Biological fermentation using organic waste substrate is one stop solution for problems including organic waste treatment, energy crisis and pollution due to over dependency of fossil fuel, fluctuating fuel price due to limited reserve in localized geographical location and regional tension. The increasing food waste generation and inefficient disposal leads to environmental pollution. Considering the problem, current study aims for H2 production in dark, photo, sequential and single stage dark-photo fermentation (SSDPF) with carbohydrate concentration (1-5 g L-1) from wheat grain waste employing Enterobacter aerogenes MTCC 2822 in dark fermentation and Rhodobacter sphaeroides O.U.001 in photo fermentation. A maximum H2 yield of 270 mL H2 g- 1 carbohydrate was achieved in SSDPF followed by 170 and 160 mL g-1 in photo and dark fermentation, respectively at carbohydrate concentration 2 g L- 1. The highest cumulative H2 production was 1340 mL at carbohydrate concentration 4 g L-1 in SSDPF. A pH drop till 4.6 was observed at carbohydrate concentration 5 g L-1 in dark fermentation. With dark fermentative effluent (DFE) as substrate, pH was increased up to 9 during photo fermentation and H2 yield was 45.8 mL H2 g- 1 TVFA at an initial TVFA concentration 1.6 g L-1. Further 3% increase in electron partition towards H2 was achieved in SSDPF process, which shows SSDF process has higher efficiency compared to individual dark or photo fermentation.